Effect of thawing procedures on fertility of bovine spermatozoa frozen in .25-ml straws.

The influence of thawing procedures on fertility of semen in .25-ml Continental 3 straws was investigated in a series of eight trials utilizing 1,634 cows. The following pregnancy rates were obtained: Trial 1, 38.6 vs 23.0% (P<.05) for semen thawed in 75 C water/7 sec vs "in the cow"; Trial 2, 29.7 vs 22.2% (P>.10) for semen thawed in 75 C water/7 sec vs "in the cow"; Trial 3, 82.8 vs 61.6% (P<.01) for semen thawed in 75 C water/7 sec vs "in the pocket"; Trial 4, 49.1 vs 45.9 (P>.10) for semen thawed in 75 C water/7 sec vs 3 C water/2 min; and Trial 5, 55.3 vs 56.0% (P>.10) for semen thawed in 75 C water/7 sec vs 35 C water/12 sec, respectively. Three of the eight trials were conducted to compare the fertility of semen used immediately after thawing or after incubation in iced water (3 C) for 10 minutes. All semen was thawed in water at 35 C/12 sec (Trial 6) or 75 C/7 sec (Trials 7 and 8). The pregnancy rates were as follows: Trial 6, 62.7 vs 47.6% (P<.05); Trial 7, 65.5 vs 59.7% (P>.10) and Trial 8, 70.8 vs 70.0% (P>.10), for semen used immediately or after 10 min of holding, respectively. It was concluded that thawing "in the cow" or "in the pocket" was unaccept-